Abstract:

Whole body vibration (WBV) is widely used as a mechanical stimulus for neuromuscular training, and to a lesser extent, in the treatment of patients undergoing physical rehabilitation. PURPOSE: To quantify any beneficial and/or synergistic effects associated with the longitudinal administration of WBV and progressive resistance (PRE) exercise on lower extremity strength development and postural stability. METHODS: We recruited 30 physically-active men (age, 22.2±3.2 yrs; hgt, 178.9±6.1 cm; mass, 75.8±7.2 kg) who had not participated in resistance training activities during the past 3 months and had no history of lower extremity injury. Participants were randomly assigned to one of three groups: WBV = PRE squat exercises with WBV (n=10); NO WBV = PRE squat exercises without WBV (n=10), or CONTROL (n=10). For those in the WBV and NO WBV groups, the experimental treatment consisted of 24 sessions of progressively-loaded squat exercises (3 sessions per week x 8 weeks) using weighted vests. A computerized posturography
device was used to administer the modified Clinical Test of Sensory Interaction on Balance (mCTSIB) that quantified sway velocity. An isokinetic dynamometer was used to obtain concentric and eccentric peak torque values at 60°/sec, 120°/sec and 180°/sec during a unilateral, closed kinetic chain (CKC) leg press. All groups were tested at entry (Week 0), midpoint (Week 4), and upon conclusion of the study (Week 8). RESULTS: The mCTSIB scores (foam box/eyes open condition) were significantly better in the WBV group compared to CONTROL when measured at Week 4 (WBV = 0.46±0.01°/sec, CONTROL = 0.56±0.01°/sec; p=0.004) and at Week 8 (WBV = 0.49±0.01°/sec, CONTROL = 0.55±0.12°/sec; p=0.036). For the right limb, concentric leg press peak torques (normalized to Nm/kg body mass) increased at 60o/sec from 0.84±0.43 Nm/kg at Week 0 to 1.10±0.47 Nm/kg at Week 8 (p=0.03), and at 180°/sec from 0.82±0.37 Nm/kg at Week 0 to 1.03±0.36 Nm/kg at Week 8 (p=0.018). There were no significant Group differences observed for any of the CKC leg press measures (p > 0.05). CONCLUSION: While the 8-week training protocol was shown to be an effective means of improving both postural stability and isokinetic leg press strength, long-term exposure to WBV did not enhance lower extremity strength acquisition among the participants.